1. Field of the Invention
This invention relates to a disc playback device and a disc recording device, and more particularly to a disc playback device for playback of discs in which sound having a super audio-frequency signal range up to 40 kHz have been already recorded into separate left channel signals and right channel signals respectively and a disc recording device for recording sounds having a super audio-frequency signal range up to 40 kHz which is also separated into left channel signals and right channel signals up to 40 kHz onto a disc.
2. Description of the Prior Art
CD (compact disc) as a digital audio disc has great advantages, for example a high quality sound, an improved dynamic range and a decreased distortion when compared to a conventional record such as LP (long-playing record). Moreover, the CD is a small-sized recording medium. Thereby the CD is the most widely applied to deal with the digital audio disc. In addition, the CD can be executed with high concentration recording in which left channel signals and right channel signals of audio-frequency signal range up to about 20 kHz are recorded by using a sampling frequency of nearly 44 kHz. The signals can be recorded for a maximum of 70 minutes per a CD. In the CD, the left channel signals and the right channel signals are recorded under a state in which these signals are composed of a plurality of frames as channel-bits transformed from data-bits having 264 bits per one data-bit to channel-bits having 588 bits per one frame by using EFM (Eight to fourteen modulation) as shown in FIG. 1. The channel bit (588 bits) is composed of a frame syncronism pattern (24 bits and 3 bits for connection), a users-bit (14 bits and 3 bits for connection), two information-bits (168 bits and 36 bits for connection) and two error correction bits (56 bits and 12 bits for connection) for one left channel signal and one right channel signal.
In this case, a bit-rate is about 1.936 Mbit/sec. Namely, the sound of the audio-frequency is recorded in the conventional CD by using the signal frame of 588 bits per one signal frame. This makes it difficult to record sound with audio-frequencies of more than 20 kHz.
While, they say that it is difficult for a person to hear sound over 20 kHz. The sound is transmitted to the brain through the skin near the ears and the skeletons of inner ears, thereby it is known that .alpha.-waves are increased in the brain of a person by hearing the sound of audio-frequency signal range over 20 kHz.
As mentioned above, it is difficult to record the sound of the audio-frequency signal range over 20 kHz by using signal frames comprising 588 bits per one frame. Recently, there have been strong demands for extending sounds having a super audio-frequency signal range to about 40 kHz for increasing the .alpha.-waves in the brain of a person.